1. Field of the Invention
This invention relates to methods for processing elastomer composite on a roll mill and apparatus therefor.
2. Description of the Related Art
The horizontal two roll mill, often called an open mill, is commonly used in the rubber and plastics industry to masticate polymer-based materials. In general, the mill includes two cylindrical rolls situated in or close to a single horizontal plane. The rolls are hollow and may be heated or cooled. The two rolls need not be the same size and may be rotated at the same or different speeds.
In processing viscous materials such as elastomer composites, the material being worked on the mill may not adhere to the roll properly; in such cases, an operator must reach under the roll, grab the end of the material and bring it back to the surface of the roll or all the way up to the nip between the two rolls. In operating the mill, differences in surface speed between the two rolls causes the material to gather on one of rolls, where it is masticated by the other roll. Some rubbers may gather on the “wrong” roll initially, e.g., at startup, whereupon the operator must cut the material from the “wrong” roll and feed the end of the cut material over the proper roll.
Even normal mastication procedures may require the material to be cut and re-fed over the roll or into the nip between the rolls. For example, when elastomer composite is compounded, the material may be cut to allow a portion of the banded material to come off the roll away from the band. Depending on how the material is cut, the material may pick itself up and feed into the nip, or the operator may have to feed the end of the strip into the nip. This operation facilitates addition of fresh material to the mill and exchange of material between that banked over the nip and that banded on the roll. It is thought that this re-feeding of the material into the nip ensures adequate levels of mastication (see, e.g., “Safe Use of the Horizontal Two Roll Mill”, New Zealand Department of Labour, 1984, available at www.osh.dol.govt.nz/order/catalogue/tworollmill.shtml).
To achieve higher throughput, it is desirable to operate the roll mill at higher surface speeds. However, the need for a human operator reduces the maximum safe roll surface speed. Furthermore, it may be desirable to automate operation of the roll mill even at lower speeds. However, the roll mill must be configured to operate without manual manipulation of the material being processed.